1. Field of the Invention
This invention relates to a system and process and apparatus for the detection of flaws in eggs.
2. Description of the Prior Art
Modern, high speed, egg grading packing machines handle up to 40,000 eggs per hour. This number of eggs causes considerable problems in their inspection for hair cracks and other flaws. Although a large number of automatic inspection devices have been proposed, candling of eggs still tends to be by human inspectors by examination in a light compartment. When the number of eggs is large, the number of inspectors must also be large and design of the candling chambers is therefore difficult. Moreover, there is an upper limit to the accuracy and speed at which the inspectors can operate because of the concentration required. Fatigue is a major factor. Thus, one disadvantage of this method for the detection of flawed eggs, is that the expenditure at personnel is relatively high and that, moreover, in practice only about half of the flawed eggs are discovered.
Various automated systems that have been tried include tapping of eggs so that a flaw can be recognized from the type of sound which develops from the tapping, (see for example, Canadian Patent No. 927,965 issued Jun. 5, 1973 to Bliss). Alternatively the change in elastic characteristics can be noted by tapping with a small hammer which bounces back less far from places which are not cracked, (see for example Dutch Patent Application No. 286,485). If an egg is vibrated, a damping of the vibration on the flawed places can be detected.
Examples of previous patents or patent applications which have attempted to solve the problems are as follows:
East German Application No. 293,340, published Aug. 29, 1991 disclosed utilizing the intensity of light transmitted through eggs as a criterion to distinguish between flawed and perfect eggs.
European Patent Application No. 373,261, published Jun. 20, 1990, disclosed locating the eggs on a conveyor roller track at high speed while examining them by a detector. Flawed eggs are discharged from the conveyor at a appropriate position downstream of the inspection station. European Patent Application No. 373,261 is assigned Staalkat BV.
Dutch Patent Application No. 8,303,804, published Jun. 3, 1985 and assigned to Vulcaan BV provides a system for alleviating operator eye strain.
U.S. Pat. No. 4,487,321, issued Dec. 11, 1984 to Bliss, utilizes an elongated pointer for movement into and out of engagement with eggs. Signal generators respond to pointer movement for generating signals for identifying the position of selected articles when they are engaged by the pointer.
U.S. Pat. No. 4,182,571 issued Jan. 8, 1980 to Furuta et al, utilizes light reflection signals obtained from light beams passed through an egg to select blood containing eggs.
U.S. Pat. No. 4,161,366 to Bol et al and issued Jul. 17, 1979, utilizes a laser as a light source to scan the egg. The intensity of light penetrating into the egg is measured. The light penetrating into the egg is partly diffusively reflected, partly absorbed while entering the shell particularly in the case of brown egg shells. Another part of the light gets inside the egg and is strongly scattered by the shell structures. This latter light is dissipated by multiple reflections of the inner surface of the shell and of the yoke sac. The egg glows uniformly. The light radiating from the egg corresponds to the structure of the shell. In particular, the egg shines more brightly when the scanning light beam falls on thin, glassy spots of the shell or an cracks. An actual flash of light may be observed.
The process and system of the invention of U.S. Pat. No. 4,161,366 is of considerable interest in the potential automation of egg candling. However, the characteristic flash of light produced by the process is produced not only by cracks but also by pin holes and regions of thin shell such as cage marks or body checks. Some of these flaws may be acceptable but actual open cracks never are. It is therefore, important to distinguish between cracks and other flaws.
In order to devise a system which will operate in real time at the speeds of the egg handling equipment, it is necessary to be able to distinguish between cracks and other flaws very fast.
The present inventors have addressed the problem of distinguishing cracks from other flaws.